A common amplifier configuration used in electronic instruments is the differential amplifier. Typically, such differential amplifiers comprise a pair of transistors having their emitters coupled together via a resistive-capacitive (RC) network, wherein an input signal is applied across the bases of such pair of transistors and an output signal is developed across the collectors. It is a common technique to provide an adjustable capacitor in the RC network to allow adjustment of high-frequency compensation or high-frequency response of the amplifier.
It has become advantageous for many reasons to implement wideband amplifiers in integrated circuits. Even so, certain circuit elements, also known as discrete components, have had to remain outside the integrated circuit package, either because they cannot be conveniently implemented, or because they involve selection or adjustment as dictated by the operating environment. One such discrete component is the aforementioned adjustable capacitor, which because of associated lead inductance and packaging parasitic capacitances, makes high-frequency adjustments for the amplifier a difficult and often tedious task.